In mattress and cushion construction, a need has been recognized for mattresses or cushions which provide comfortable and durable supporting surfaces, but are also cost-effective to produce.
A variety of configurations have been used to provide such optimum sleeping surfaces. Some mattress configurations have included types of foam rubber to provide a cushioning effect to support the human body. Other configurations have utilized a plurality of spaced-apart coil springs, which, depending on the user, provide support preferred to that provided by foam rubber only.
Spring Assemblies
One example of such a spaced-apart coil spring assembly is U.S. Pat. No. 4,051,567 to Hutchinson, which discloses a coil spring assembly including aligned rows of coil springs connected together within each row and between rows, and also includes additional reinforcing springs which are interspersed about the periphery of the spring assembly, with all springs being held in place by a border helical and helical tie wires. Although such mattress configurations are effective, disadvantages are apparent in that such linked configurations do not allow for independent action of the springs, thus preventing the mattress from conforming accurately to the user's body.
Pocketed Coil Springs
It has also been known to provide springs in a preloaded state, prior to assembly of the springs into a mattress or cushion construction. The preloaded configuration of the springs provides a supporting structure that is sufficiently yielding to be comfortable but does not deflect excessively as would a cushion or other structure composed of similarly configured but non-preloaded springs.
One example of such constructions is in U.S. Pat. No. 1,466,617 to Foster, entitled "COVERED SPRING STRUCTURE", discloses a tubular covering formed on flexible material such as cotton cloth or the like, provided by bringing opposite edges of a long strip of cloth together and sewing through both layers of cloth near the adjacent edges by a row of stitches. The length of the tubular material is then cut into individual units of a desired length by cutting the long tube along dotted lines 16, illustrated in FIG. 1. Springs are then provided into the individual tubular coverings such that they can then expand into a semi-compressed state. The covered springs are then assembled side-by-side and then fastened by fastening means such as U-shaped metal clips. The feature of having the springs held under partial compression provides a structure that is sufficiently yielding to be comfortable but without the great extent of sag or give before the person is sustained that is present in a cushion or other structure composed of equally soft or resilient springs. It may be seen that the covered spring structures shown in Foster include narrow strips 17 of material beyond the stitches 15, which may extend in a radial direction relative to the longitudinal axes of the springs, or may extend in a generally axial direction (column 2, line 103-column 1, line 3). It should be noted that Foster provides that "[a]s far as convenient in assembling, this seam will be placed at the top or bottom of the tube when the tube and the spring are assembled (col. 2, lines 4-7). Another feature of the individual tubular coverings is that the covering they provide may prevent wear or noise from the springs (p 2, lines 122-124).
Pocketed Coil Strings
In order to provide improved handling characteristics, it has been known to provide "strings" of pocketed coil springs, wherein the springs are encapsulated in a preloaded state within pockets formed in an elongate strip of fabric, the axes of the springs being generally parallel to each other. For purposes of this application such configurations will be referred to as "pocketed coil strings". It should also be understood that the terms "coil", "spring", and coil spring are interchangeable for purposes of this discussion.
As discussed in greater detail later in this application, such pocketed coil strings may be aligned with and attached to other coil strings by various attachment means, in order to provide mattress or cushion assemblies.
Radially Extending Seams
U.S. Pat. No. 3,462,779 to Thompson, entitled "CUSHION" includes strings of coils disposed intermediate resilient deformable layers of material which may be foam rubber. Each coil string is formed as shown in Thompson's FIG. 3, wherein individual springs are first positioned in a side-by-side relationship, durable spring covering material is then placed above and below the springs, and finally seams are sewn about the periphery of the row of springs, and also intermediate each spring, thus encapsulating each spring. It should be noted that such a configuration includes a outwardly-disposed seam 38, which extends the length of each of the coil strings in a generally radial method relative to the longitudinal axes of the springs. As it may be understood that such an outwardly-disposed seam extends radially relative to the longitudinal axis of the springs, such seams will now be referred to as "radially" extending seams. The disadvantages of these seams are evident in that it may be seen that the seams may interfere with the seams of adjacently-situated strings. Further disadvantages exist in that excessive pocket materials are required to fabricate the pocketed coil strings, especially for taller spring configurations.
Axially Extending Seams
In my U.S. Pat. No. 4,234,983, entitled "THERMALLY WELDED SPRING POCKETS", pocketed coil strings are provided, in which the individual springs are formed between the overlaid plies of a two-ply strip of material by lines of separate individual thermal welds which connect the plies together. It should be noted that such configurations include a seam which extends along one end of the springs. For purposes of this application, such a configuration will be referred to as having an "axially"-extending seam, as the seam (or seams) extends in an axial manner along the longitudinal axes of the springs.
Pocketed Coil String Manufacture
In my U.S. Pat. No. 4,439,977, entitled "METHOD AND APPARATUS FOR MAKING A SERIES OF POCKETED COIL SPRINGS", a method and apparatus are disclosed for making coil springs pocketed within individual pockets in an elongate fabric strip comprised of two overlaying plies capable of being thermally welded together. The fabric strip is fed along a guide path during which compressed springs are inserted between the plies with the axes of the springs substantially normal to the planes of the plies, whereafter the fabric plies are thermally welded together longitudinally and transversely to form a string of pocketed coils. After thermal welding, the pocketed coils are passed through a turner assembly during which the springs are reoriented within the fabric pockets to positions wherein the axes of the springs are transverse to the fabric strip. Although this method of manufacture has several advantages, one disadvantage is that, during the turning process, the springs may tend to become "hooked" on themselves, and do not extend to their proper positions. Therefore, additional and costly labor is required to orient the "hooked" springs to their desired configurations. Even if the springs do not become " hooked", difficulties may still arise in correctly aligning them to their desired positions, with the longitudinal axes of the springs being substantially parallel.
Assemblies of Strings of Pocketed Coils
As previously discussed, pocketed coil strings may be readily assembled into mattress or cushion assemblies. An example of the use of such strings is shown in my U.S. Pat. Nos. 4,234,984, entitled "POCKETED SPRING ASSEMBLY" and 4,401,501, entitled "APPARATUS FOR MAKING ASSEMBLIES OF POCKETED SPRINGS" in which strips of pocketed upholstery springs are assembled, one strip at a time, into mattresses and the like. The connections of each such strip to its predecessor are made between the interpocket webs of the pocket sheeting of the two adjacent strips, preferably at intervals of two springs, and are staggered by one spring from strip to strip. The disclosed and preferred technique for joining the pocket material of the adjacent strips is thermal welding by ultrasonic vibration, but other specific forms of connection are also suggested.
In my U.S. Pat. No. 4,451,946, entitled "POCKETED SPRING ASSEMBLY", an improvement of my U.S. Pat. No. 4,234,984 is discussed. The improvement includes an elongated connection which connects the pocket sheeting of adjacent strips together between adjacent springs of a strip, with the firmness of the assembly thus being increased by the nature of the elongated interstrip connection.
In my U.S. Pat. No. 4,523,344, entitled "INDEPENDENT BLOCK ASSEMBLY OF SPRINGS", a spring assembly is disclosed which includes a plurality of interconnected longitudinal blocks of pocketed coil springs. each block includes a pair of interconnected strips of pocketed springs which are preferably arranged in a square array. Each pair of strips is tightly encased by a flexible cover. The covers are connected to each other along longitudinal hinge lines which allows the assembly to bend easily in at least one direction.
In my U.S. Pat. No. 4,578,834, entitled "INNERSPRING CONSTRUCTION", an innerspring construction including adhered strings of pocketed coil springs is disclosed together with a method of manufacture. The strings are connected to each other by an adhesive applied between the lines of tangency of adjacent coil springs. A hot melt adhesive applicator traverses a string of pocketed coils, depositing a precise amount of adhesive on each coil jacket. A second string is positioned on the first, and pressure is applied thereto. The applicator then traverses the second string in the same manner as the first. The sequence is repeated until an innerspring construction of desired size is created. My U.S. Pat. No. 4,566,926, entitled "METHOD AND APPARATUS FOR MANUFACTURING INNERSPRING CONSTRUCTIONS", a continuation in part of U.S. Pat. No. 4,578,834, discloses the method and apparatus for manufacturing the mattress assembly disclosed in U.S. Pat. No. 4,578,834.
Miscellaneous Approaches
In U.S. Pat. No. 3,668,816, entitled "METHOD AND APPARATUS FOR CONSTRUCTING FABRIC ENCLOSED SPRINGS", strips of web material are longitudinally folded for receiving compressed coil springs therebetween. The fabric is first folded along a longitudinal fold line 37, forming a two-ply configuration with one ply 36 being somewhat wider than the second play 34. Axially compressed springs are then inserted between the plies in spaced-apart relation. Transverse sew lines are then provided to the fabric with the springs still compressed, thus sewing the plies 34, 36, together and forming "pockets" of fabric with one open side, that side being along the longitudinal edges of the fabric. With the springs still in their fully-compressed state, the portion of ply 36 which extends over ply 34 receives adhesive and is then folded over ply 36 at 80, thus completely closing the pockets of fabric with the springs inside. The springs are later allowed to open into the configuration shown in FIG. 8. Although the longitudinal seam of the pocketed coil springs do not extend axially or radially, it may be seen that this configuration requires the springs to be severely compressed during their insertion. Similarly, waste of material is evident as shown in the final configuration of FIG. 8, in which the transverse sew liens are not parallel to the longitudinal axes of the springs, but instead are orthogonal to the longitudinal axes of the springs, thus requiring the fabric to buckle and wrinkle to accommodate the springs.
In U.S. Pat. No. 4,485,506, in which I was a co-inventor, entitled "COIL SPRING CONSTRUCTION", a coil spring construction is provided for incorporation within a mattress or a cushion. The construction includes a plurality of independently mounted pocketed coil springs. Resilient stabilizers are provided between the springs to maintain their axial positions. The spring pockets are formed by the sealing of first and second sheets to each other in a substantially circular configuration about the longitudinal axis of the spring. Spring height is determined by the inside diameter of the seal. It should be noted that this disclosure notes that one advantage of this method is that the springs may simply be allowed to expand after insertion and do not require turning. As previously discussed, in methods where compressed springs are inserted into folded strips which are then stitched or welded in a rectangular pattern, the springs must be turned after insertion so that their axes are substantially colinear with the longitudinal axes of the resulting pockets. (col. 2, lines 49-60).
Disadvantages in the Prior Art
Although the above-discussed patents provide configurations which include distinct advantages, it should be understood that some shortcomings do also exist, especially in light of the methods used in assembling the strings into mattress or cushion configurations. It should be understood that the pocketed coil strings which include radially-extending seams such as those shown in U.S. Pat. No. 3,462,779, can present difficulties when positioned alongside similar strings, as the seams can prevent the sides of the springs from being closely positioned adjacent to each other. However, pocketed coil strings having axially-extending seams such as that shown in my U.S. Pat. No. 4,234,983, although possessing distinct advantages, can produce a phenomenon known as "false loft" when positioned alongside other strings to provide a cushion or mattress as shown in my U.S. Pat. No. 4,578,834.
When comprehending "false loft", one should understand that mattress construction such as that described in U.S. Pat. No. 4,578,834 typically include the above-described spring base, with at least one layer of fabric positioned intermediate the ends of the springs and the intended sleeping surface. False loft occurs when the axially-extending seams maintain the cover material a certain distance away from the ends of the springs. When the mattress is first purchased, this distance is fairly uniform. However, after the mattress or cushion has been in use for a period of time, the axially-extending seams may become "crushed", thus leaving a type of body depression. With continued use of the mattress or cushion, entire support surface of the mattress or cushion will similarly be crushed, and the support surface of the mattress or cushion will then appear substantially flat. However, the customer, upon observing a body depression, may not realize that the support surface will flatten out with time, and may interpret the body depression as being a mattress or cushion defect, which may result in the mattress or cushion being returned to the point of sale. Although the customer may be subsequently educated as to the phenomenon of "false loft", it would extremely advantageous to provide a mattress or cushion configuration which does not exhibit such a a mattress or cushion configuration which does not exibit such a phenomenon.
The configurations which require the springs to undergo severe axial compression during insertion into fabric pockets possess severe disadvantages as they may allow the springs to become tangled or "hooked" on themselves instead of expanding to their desired position. Therefore additional labor is required to "unhook" the springs to allow them to expand as desired.
Finally, the configurations which require turning of the springs after insertion into the pockets also possess disadvantages in that the springs may not be accurately positioned during the turning process, thus resulting in the assembly of pocketed coil strings which may have springs which are not axially aligned.
Therefore, it may be seen that a need exists for a pocketed coil string which overcomes the disadvantages in the prior art by providing a seam configuration which does not interfere with the assembly of the coil strings alongside similar coil strings, and also does not provide the phenomenon known as "false loft". Furthermore, it can be seen that a need exists for a method of assembly of pocketed coil strings which does not require turning of the springs after insertion of the springs into their respective pockets. Finally, a need has always existed to provide mattress materials which are cost-and-labor effective in that they require a minimum amount of materials and labor.